Most commercial aircraft require more antennas than in the past to accommodate a variety of required operating frequencies. As more antenna elements are deployed on an aircraft, existing electronics-based networking systems may not be the best way to route digital and analog signals because of the significant volume of electronic cables required to accommodate each antenna. The higher mass of cables would reduce fuel efficiency, increase electromagnetic interference, and make cable repair and maintenance more difficult. As an alternative, NASA Glenn Research Center’s Satellite Network and Architecture Branch developed a radiofrequency/optical networking subsystem for data and voice transmission that reduces the adverse effects caused by conventional electronic subsystems.
Architecture of radiofrequency/optical backbone network suitable for supporting numerous antenna elements on an aircraft.
Long description of figure.
The diagram shows the architecture of a radiofrequency/optical backbone network for supporting multiple antenna elements on an aircraft. There are six physical layers constructed in this architecture: the antenna, the protocol converter, a transceiver, protection and working fibers, another transceiver, and the hub and switch module. Protection and restoration data paths are used to prevent data loss in case of cable failure, port failure, or catastrophic failures. The architecture is based on the optical wavelength division multiplexing approach, which can support different types of protocols such as synchronous optical network (SONET)/synchronous digital hierarchy (SDH) time-division multiplexing, Ethernet system, and asynchronous-transfer-mode- (ATM-) packaging-based or cell multiplexing systems.
Two popular transport protocols proposed for the aircraft’s networking backbones are SONET and wavelength division multiplexing (WDM). SONET has a number of advantages over other optical protocols, such as (1) less equipment needed, (2) increased network reliability, (3) easy access for switching and multiplexing, and (4) a flexible architecture to accommodate future requirements.
WDM relies on the fact that an increased number of wavelengths on a fiber tends to enhance the bit rate of network systems. A major attractive feature of the WDM structure is that each individual wavelength can use a different protocol for transport. For example, we could use one wavelength for SONET, a second for optical gigabit Ethernet, and a third for ATM. Such a WDM structure saves costs because just one amplifier can act upon all wavelengths. Most WDM equipment can support different types of interfaces, such as SONET, Ethernet (1 gigabit per second (Gbps), 10 Gbps, and fast), fiber channel, and ATM.
Glenn contacts: Dr. Hung D. Nguyen, 216-433-6590, Hung.D.Nguyen@nasa.gov; and Calvin T. Ramos, 216-433-9391, Calvin.T.Ramos@nasa.govLast updated: October 6, 2006
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